Surveillance cameras used to monitor a specific setting may from time to time need additional lighting to be able to give a good picture of the environment they monitor. This is for instance the case during night time in an outdoor setting when the natural light is insufficient for the camera. Some type of lighting can then be used in combination with the surveillance camera. A common choice of light sources is light emitting diodes (LEDs) emitting infrared or white light, for illuminating the scene which is monitored by the surveillance camera.
A problem when using a light source in the camera is that it tends to generate a lot of waste heat, which in turn may have a negative impact on the performance of an image sensor in the camera, especially if the light source is integrated in the camera.
Another issue is that the illumination provided by a camera integrated light source or an external light source is often not reconfigurable or adaptable when the installation has been finished without physically replacing the light source. Instead, prior to the actual installation of the surveillance camera, a proper range of the illumination to match the imaging conditions in the installations needs to be determined in advance, and this can be a cumbersome task requiring a lot of effort in some cases. This is often what is done when installing a fixed focus camera, having fixed imaging settings of the optics during operation.
However, in a varifocal camera, it is not feasible to the same extent to choose a setting for the lighting in advance, as these cameras alter the zoom and focus position dynamically during operation. A light source that has a long and wide range, in order to cover all possible distances of interest for the particular camera during operation, is often chosen for varifocal cameras. However, this results in high power consumption as well as more heat generation than necessary for most of the operation time.
The problems with the excessive heat generation and power consumption may be reduced if lighting can be controlled to match the camera's need of light.
EP 2 490 439 discloses an illumination device for illuminating a scene monitored by a camera. The device has a plurality of LEDs associated with a plurality of lenses. Depending on area to be illuminated, the suitable LED and lens configuration is selected.